Polar Opposites – When Compasses Go Bad

I’m one of those lucky people who has an in-built compass that most times just knows instinctively which way is North. I think I got it from my Dad, as opposed to my Mum who was from the ‘turn-the-street-directory [remember those?] around-until-it makes-sense-and-then-stop-to-ask-for-directions’, school of navigation.

So it was no surprise that on last weekend’s trip to the beautiful Coxs River, I thought my inbuilt compass had gone a little wonky.

Which one of these is not like the other one?

The toppo map, the bend in the river, my inbuilt compass and my trusty reliable Silva compass seemed to be conspiring against my sense of sanity.

I couldn’t understand why Goolara Peak was behind us… it should be in front of us! This doesn’t makes sense.

It was only when my friend Helen came along and we conferred that things suddenly became crystal clear. The photo above says it all. Her compass is the one on the left, whereas mine on the right is showing exactly the opposite. Double confirmed by the electronic compass in my watch.

Who moved Goolara Peak? [Upstream on the Coxs River]

I emailed Silva [Sweden, not the USA company] to find out how to fix this. I’ve heard it’s as easy as wafting a magnet nearby. Here’s the response:

“The reason that your compass is not showing north is most likely due to it being subjected to a magnetic field that has polarized the needle. This is, unfortunately, fairly common in today’s world since we carry a lot of items that emit a magnetic field such as mobile phones, GPS and other equipment. A compass needle cannot change its own polarization, it has to be “forced” to reverse its polarity by a magnetic field.

We write in the manual that it is very important to check the compass every time it is used since polarizations do happen, it is as important as checking any part of your survival gear before it is used, since your life may very well depend on its functions. [Lotsa: Couldn’t agree more… now!]

It is not complicated to reverse the polarization of the needle but to be 100% sure of the result you should be using a controlled magnetic field. Because of this I do not recommend that you polarize your compass by yourself, if you send your compass to us here at Silva Sweden AB we can polarize your compass free of charge, the only cost for you is to ship the compass to us.” (David, Technical Support, Silva)

And so, today my compass which has served me well and I’ve trusted implicitly (until last weekend) will be going on a little Scandinavian holiday…

… I can’t help but think about all the magnetic fields in the aircraft and postal sorting machines between here and Sweden though!

I have numerous compasses, a bit of a collector, and have also noticed this but only on Silva compasses so far. None of the Suuntos that I’ve seen have had this problem??? Retentivity is the property of the alloy used to make the needles that maintains it’s strength and polarity. I’m starting to wonder if the Sunntos use a better alloy? Please pass on any experience you may have had with polarity reversal.

Graeme I would not be sure that a compass needle that has inverted its magnetic polarity would align exactly south or would retain it’s current polarity. Walking in remote areas I need to be able to trust my compass.

Magnet in a Mobile Phone ??? – maybe if you use a case that has a magnetic latch. There are tiny magnets to hold in stylus. My phone has an Electronic Compass inside it – if it had a magnet strong enough to affect an external compass, it would ruin the internal compass.

Beware of putting your Emergency Beacon near anything with a magnet – some PLBs are activated by a magnet !

My friend it is not a magnet they’re referring to with the phone or GPS units. It’s the fact that every single electronic device, including a simple wire with a tiny current passing through it on its way somewhere else, emits a “magnetic field”. It is this field that affects any compass kept near to it.

A while ago 2 of us were taking bearing on mountains and walking set bearings. My friend was always about 15 degrees different. He complained that he had had a few of his compasses (he was now onto his 5th!!) change polarity.

We finally worked out the problem … his special “outdoor shirt” had some great pocket clips … little magnets to keep them closed. Guess where he used to store his magnet …? String looped around his neck and then compass in his top pocket.

Had the same problem with a magnetised mouthpiece on a bladder hose that ‘attached’ to magnet on the sternum strap. Everytime the mouthpiece swung from side to side over the top of my compass – it remagnetised it. Solution was to prise out the magnet embedded in the mouthpiece.

Hi, I have two Silva compasses which have just reversed. I do much of my walking Munro bagging in Scotland, where I can be in the cloud for hours on end. I always carry two compasses. I leave my last bearing on one and put the latest bearing on the other. That way if anything goes wrong I can reverse the compass and re-tread my steps along the bearing I actually used rather than the one I might have thought that I used. So I need the polarity to be right. I am also finding that the magnetism in the reversed polarity mode is reduced. The needles seem to be floating about rather than ‘nailing’ the bearing. Best, John.

Great idea, John. It’s when you’re in a white-out that compasses prove themselves to be the valuable piece of kit that they are. I’ve heard of GPS units even struggling in thick fog… but I’m not convinced about that. Keep bagging!

Hi, I have had this happen more than once with Silva compasses; please see my earlier comments. I sent several compasses to Sweden and they have come back quite quickly and pointing in the right direction. Unfortunately I haven’t worked out the cause in my case (I think it might be my yacht) and the change in polarisation has happened again on my favourite Silva compass. I think this may turn out to be a regular event. Best to all, John.

Hello All, I just had the same magnetic reversal of my tried and true Brunton Style 15 pocket compass. I will ask Brunton if they can fix it. I think in my case, it was either Iphone or GPS unit. I was packing with both of them. I thought I had lost all sense of my innate sense of direction.